Reversing drive mechanism for cleaning-air tubes in selfcleaning filters



1952 w. M. SHELDON 2,584,746

REVERSING DRIVE MECHANISM FOR CLEANING-AIR TUBES IN SELF-CLEANING FILTERS Filed Sept. 10, 1949 s Sheets-Sheet 1 INVENTOR.

AA 6/3 Arm/1w Feb. 5, 1952 w. SHELDON 2,584,746

REVERSING DRIVE CHANISM FOR CLEANING-AIR TUBES IN SELF-CLEANING FILTERS Filed Sept. 10, 1949 5 Sheets-Sheet 2 4 3; I Z! r IN V EN TOR.

Feb. 5, 1952 w' M. SHELDON 2,584,746

REVERSING DRIVE MECHANISM FOR CLEANING-AIR TUBES IN SELF-CLEANING FILTERS Filed Sept. 10, 1949 3 Sheefcs-Sheef 3 INVENTOR.

Patented Feb. 5, 1952 BEVERSING DRIVE MECHANISM FOR CLEANING-AIR TUBES IN SELF- CLEANING iLTE William M. Sheldon, Elizabeth, N. J., assignor to Pulverizing Machinery company, Summit, N. .I., a co p a i n of Ne s y Application September 10, 1949, Serial No. 115,038 3 Claims.' (01. 1837-61) This invention relates to drive mechanism for cleaning-air tubes in self-cleaning filters of the type in which the air to be filtered passes outwardly through a layer of suitable material, usually felt. Usually the filtering material is cylindrical in form, in which case the cleaning-air tube is,ring-shaped. For convenience, the invention will be described as applied to a cylindrical filter with a ring-shaped cleaning-air tube, usually termed a blow-ring. However, it is not intended thereby to restrict the scope of the invention to filters of that particular construction.

The blow-ring is slotted or perforated on its inner side where it contacts the tube so that by supplying compressed air to the ring such'air can be forced inwardly through the felt from the outside to clean the felt. To prevent lateral escape of the cleaning air, the blow-ring is made of slightly smaller diameter than the filter cylinder so that, due to the internal air pressure in the cylinder, the filter material is pressed outwardly against the blow-ring.

The filter cylinder is vertically arranged with a hopper attached to its lower end for the collection of the separated dust. The blow-ring is reciprocated up and down the outside of the filter cylinder to keep the latter permeable to air. Chains or cables have been used for reciprocating the ring. Where chains are used, theirdriving sprockets can be either rotated continuously in one direction or rotated first in one direction and then in another.

With the first arrangement, one link of the chain has a pin extending laterally from it to clear the sprockets and to the free end of the pin is pivotally attached one end of a connecting member. The other end of this member is secured to the ring orto a frame carrying the ring. The pull or thrust, as the case may be, of the chain on the blow-ring is ofiset'not only at right angles to the plane of the chain as a Whole but also in such plane since on its upward movement the link carrying the pin travels along a path spaced from its downward path by the diameter of the sprocket. Consequently, it was necessary to provide guides to prevent the chain pulling the ring so that it turns first one way and then the other way about the axis of the filter tube. The provision of guides not only complicated the construction but also prevented the ring adjusting its position laterally to conform with the shape of the filter tube. The latter may, owing to poor manufacture or assembly, not be truly cylindrical. Thus, although its circumference may be substantially uniform 2 throughout, it may bow out to one side. The ring in such case should follow the bag in the shape it assumes and not the position the bag should be in.

Where the sprocket driving the chain is rotated first in one direction and then in the other, the link of the chain attached to the blow-ring never passes over the sprocket. Consequently, its point of attachment to the ring need not be oifset with respect to the central plane of the sprockets. Also as such link moves in the same path on the upstroke as well as on the downstroke, the pull on the ring is always along the same vertical line. Hence, no guide is needed to prevent the ring turning first one way and then the other way in a horizontal plane so that thering may be left free to adjust its position laterally to follow the bag. :7

It is necessary, however, to provide means for keeping the plane of the ring horizontal. if there are two chains attached at points 180 apart, the ring is balanced, but it can tilt one way or other. should be supported at three or more horizontally separated points.

A further advantage of the reversing type of drive is that it enables costly chains and sprockets to be replaced by inexpensive wire cables. Endless cables slip and do not maintain their relative positions with respect to pulleys or drums with which they are in frictional contact only. Consequently, with continuous one-direction operation, chains must be used. On the other hand, with reversing drive, the ends of the cable may be rigidly attached to the driving drum to maintain their relative positions. On the upstroke of the tube, one end of the cable unwinds while the other is wound up. On the downstroke, the operation is reversed.

Three suitable forms of construction are illustrated by way of example in the accompanyin drawings, in which:

Fig. l is a perspective, diagrammatic view of one form of drive mechanism employing chains and tension-adjusting idlers;

Fig. 2 is a side elevation of another form of chain drive mechanism;

Fig is a p an view o e f rm shown n Fie- Fig, 4 i a e le at on of a d ive me hanism using steel cables; and

Fig. 5 is a plan view of the mechanism shown in Fig. 4.

The filter shown diagrammatically in Fig. 1 comprises a felt cylinder l0 mounted on the top To prevent such tilting, the tubeof hopper H to receive the dust retained. Surrounding the felt cylinder is a cleaning-air ring l2 having a series of slots I3 around its inner periphery. Compressed air is supplied to the ring by a flexible tube 14.

The ring is suspended and drawn up and down the felt cylinder by three endless chains l8, I9 and 20, passing around sprockets 2|, 22 and 23 on a drive shaft 24 so that all three chains move simultaneously and with uniform velocity. The drive shaft is rotated first in one direction and then in the other by a motor (not shown in Fig. 1). Trip switches operated by the ring when it reaches the top and bottom of its stroke reverse the direction of rotation of the motor.

The chain l8 passes around four fixed sprockets 2|, 25, 26 and 21, and a tension-adjusting idler sprocket 28. Chain l9 passes in like manner around fixed sprockets 22, 29, 39 and 31 and idler sprocket 32. Chain passes around sprockets 23 and 33. These three chains I8, l9 and 20 are attached to the ring by pins at the points 34, and 36.

If chains I8 and I9 only were used, the ring would be free to tilt about the line joining the points 34 and 35. With the chain 29 connected to the ring midway between the points 34 and 35, there can be no tilting as the three points 34, 35 and 36 are compelled by the chains to move simultaneously and uniformly. The horizontal spacing of points 34, 35 and 36 at 0, 180 and 270 respectively, is convenient but not essential. Practically any relative horizontal spacing of the points 34, 35 and 36 will suffice to prevent tilting.

The chains is and [9, being connected to the ring at diametrically opposite points, do most of the work of moving the ring; the chain 20 acting principally as a levelling means. Therefore it is not essential to provide tension-adjusting means for the chain 20. Tension-adjusting means other than idler sprockets could be used,

- such, for example, as tension springs connected between the two ends of the chains, as shown in Fig.2.

In Figs. 2 and 3, the construction is shown less diagrammatically than in Fig. 1 and parts which were omitted in Fig. 1 to avoid obscuring the chain and sprocket arrangement are shown.

Also the tension-adjusting idlers are replaced by springs 31. So far as the parts in Figs. 2 and 3 correspond with those of Fig. 1, they have been given the same numerals.

The drive shaft 24 is provided with a worm wheel 40 driven by a worm 4| on the shaft of the motor 42. Trip switches 43 and 44 are pro- .vided for reversing the motor at each end of the stroke of the ring l2.

Dust-laden air is introduced into the top of the filter through pipe 46.

In Figs. 4 and 5' is shown a cable drive. On each side of the top of the felt cylinder is a drum 50. These drums are mounted on a common shaft 5| rotated first in one direction and then in the other by motor 52.

To each drum a cable 53 is attached at one end at the point 54. The other end of this cable is connected at 55 to the top of a diamond-shaped cable assembly 56. This assembly is attached to the blow-ring l2 at the points 51 and 58. The bottom of the assembly is attached at 59 to a second cable 60 passing down around a pulley 63 up to a spring 64 which connects it to a third cable 65 which laps around the top of the drum 50. The cable 65 is secured to the drum at the point 66. By rotating the drum first in one direction and then in the other, the cable 53 first pulls the ring upwardly and then the cables 60 and 65 pull it downwardly. It will be noted that the cable drive mechanism is connected to the blowring at four horizontally spaced points, 51, 58, 51 and 58, and the ring is consequently held in horizontal or level position. As the compressed air hose I4 is connected to the blow-ring in register with the center of one of the cable assemblies 56, its weight is uniformly distributed and has no tilting effect.

I claim:

1. A self-cleaning dust filter of the type having an annular cleaning-air tube adapted to be reciprocated to and fro vertically over the surface of a cylinder of filter medium which includes at least two flexible members passing over wheels adjacent the top of said cylinder and over wheels adjacent the bottom of said cylinder and connected to said tube at not less than three horizontally spaced points for holding said tube horizontal, all of said wheels being mounted for rotation about axes all of which are coincident with or parallel to each of the other axes, and means for imparting simultaneous uniform vertical motion to said flexible member first in one direction and then in the other to draw said tube up and pull it down alternately.

2. A self-cleaning dust filter as in claim 1 in which the flexible members consist of three chains, and two of the chains are attached to said annular tube at diametrically opposite points and the third chain is attached to the annular tube midway between the points of attachment of the first two chains.

3. A self-cleaning dust filter of the type having an annular cleaning-air tube adapted to be reciprocated to and fro vertically over a cylinder of filter medium which includes at least three continuous flexible members passing over wheels adjacent the top of said cylinder and wheels adjacent the bottom of said cylinder all of said wheels being mounted for rotation about axes all of which are coincident with or parallel to each of the other axes, said wheels also being arranged so that one flight of each of said members is vertical and parallel to the outside of said cylinder, a connection between each of said flights and the said tube and means for imparting simultaneous motion to said flights first in one direction and then in the other.

WILLIAM M. SHELDON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,944,268 Rathbun Jan. 23, 1934 2,476,942 Arnold July 19, 1949 FOREIGN PATENTS Number Country Date 652,991 France Oct. 30, 1928 209,109 Germany July 20, 1940 

